The diagram shows positive results in two different food tests - OCR Gateway - GCSE Biology - Question 8 - 2019 - Paper 3
Question 8
The diagram shows positive results in two different food tests.
Food sample plus reagent:
Treatment: shake thoroughly
Observation: black colour
Food sample plus ... show full transcript
Worked Solution & Example Answer:The diagram shows positive results in two different food tests - OCR Gateway - GCSE Biology - Question 8 - 2019 - Paper 3
Step 1
Tube 1: What does the black colour indicate?
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The black colour in Tube 1 suggests the presence of starch. When iodine is added to a starch sample, it forms a dark blue-black complex.
Step 2
Tube 2: What does the orange precipitate indicate?
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
The orange precipitate in Tube 2 is usually indicative of reducing sugars, which could suggest the presence of sugars, such as glucose or fructose, in the sample. The Benedict's test commonly gives a brick-red or orange colour for reducing sugars.
Step 3
Final Results
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Thus, the results indicate that Tube 1 contains starch and Tube 2 contains reducing sugars. According to the options provided, the answer corresponds to B: starch in Tube 1 and sugar in Tube 2.
